You need revered reputation with each of the factions before you can buy their items for this set, and the total cost for all eight items is 15000 Valor Points.

There are, however, a huge number of lookalike items available for this set throughout Mists of Pandaria, some of which are easier to obtain than the Valor purchases. You can view all of these alternatives here: Wowhead Ascendant Tribe Armor. The reason we chose to focus on the Valor items is that they are obtainable outside of raids, and represent a complete set.